SAE International Development of a High Performance Two-Cycle Engine Brake for Medium and Heavy Duty Diesel Engines 2013-01-0586

Jacobs Vehicle Systems has been leading the development of engine braking technology for more than 50 years. In order to meet the need for significantly increased vehicle retarding capability, the company focused on the development of a High Power Density (HPD) braking system. Overall vehicle retarding requirements are continuously increasing due to vehicle changes that improve fuel economy, such as increases in aerodynamic efficiency and decreases in rolling resistance, which in turn, reduce the vehicle's natural retarding. This increase in overall vehicle retarding needs comes at a time when the trend is to operate at lower engine RPM's combined with downsizing of engine displacement to improve fuel economy and reduce CO\u2082 emissions. The smaller displacement engine will clearly produce less retarding power than the larger engine it is replacing with standard engine braking technology. In anticipation of this challenge, Jacobs Vehicle Systems has developed an engine-integrated solution that will deliver large-engine braking power in small- and medium-size engines, as well as reduce the overall loading on the valve train during braking. The Jacobs' HPD brake provides for two-stroke engine braking on a four-stroke diesel engine. This maximizes braking performance, which results in an average increase of 104% in braking performance over a conventional compression-release engine brake, particularly at lower engine speeds where more than 200% gain in braking performance was measured. By distributing the braking effort over two events during the engine's full four-cycle process, the valve train loads generated during braking are reduced by as much as 30%.